6,273 research outputs found

    Dynamic output feedback linearizing control of saturated induction motors with torque per ampere ratio maximization

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    The paper presents a novel maximum torque per Ampere (MTA) controller for induction motor (IM) drives. The proposed controller exploits the concept of direct (observer based) field orientation and guarantees asymptotic torque tracking of smooth reference trajectories and maximizes the torque per Ampere ratio when the developed torque is constant or slowly varying. A dynamic output-feedback linearizing technique is employed for the torque subsystem design. In order to improve torque tracking accuracy a motor magnetizing curve is taken into account during MTA optimization and controller design. The achieved steady-state system efficiency have been compared experimentally for three types of controllers, namely: standard vector control with constant flux operation, controller based on classic maximization of torque per Ampere ratio for linear magnetic circuit and controller based on MTA strategy for saturated induction motor. It is shown experimentally that the controller designed for saturated induction motor provides not only higher torque per Ampere ratio but also increases power factor and reduces active power consumption hence improving the drive efficiency. Operation with slowly varying torque references has also been analysed. It is shown that the proposed controller is suitable for applications that do not demand an extremely fast dynamic response, for example for electric vehicle drives

    Model predictive control of a dual induction motor drive fed by a single voltage source inverter

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    In dual induction motor control applications, averaging of controlled variables, mean circuit models, or master/slave strategies are used, which lead to unbalanced and unstable operation of the overall drive system. An improved finite control set predictive torque control (FCS-PTC) method is proposed for the parallel operation of two induction motors. The optimization cost function of the controller is shown to meet multiple objectives simultaneously, eliminating the use of averaging techniques and without leading to unbalanced conditions. The simulation results are compared with direct torque control (DTC) for dual induction motors. As compared to DTC, model predictive control shows low torque and flux ripple, 5% lower current THD, improved current balancing between the motors, and negligible effect of parameter mismatch

    To develop an efficient variable speed compressor motor system

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    This research presents a proposed new method of improving the energy efficiency of a Variable Speed Drive (VSD) for induction motors. The principles of VSD are reviewed with emphasis on the efficiency and power losses associated with the operation of the variable speed compressor motor drive, particularly at low speed operation.The efficiency of induction motor when operated at rated speed and load torque is high. However at low load operation, application of the induction motor at rated flux will cause the iron losses to increase excessively, hence its efficiency will reduce dramatically. To improve this efficiency, it is essential to obtain the flux level that minimizes the total motor losses. This technique is known as an efficiency or energy optimization control method. In practice, typical of the compressor load does not require high dynamic response, therefore improvement of the efficiency optimization control that is proposed in this research is based on scalar control model.In this research, development of a new neural network controller for efficiency optimization control is proposed. The controller is designed to generate both voltage and frequency reference signals imultaneously. To achieve a robust controller from variation of motor parameters, a real-time or on-line learning algorithm based on a second order optimization Levenberg-Marquardt is employed. The simulation of the proposed controller for variable speed compressor is presented. The results obtained clearly show that the efficiency at low speed is significant increased. Besides that the speed of the motor can be maintained. Furthermore, the controller is also robust to the motor parameters variation. The simulation results are also verified by experiment

    Optimal speed and torque estimations for improving the DTC dynamic performance of induction machines

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    High-performance AC drives require accurate speed, flux, and torque estimations to provide a proper system operation. Thus, this thesis proposes a robust observer, i.e. Extended Kalman Filter (EKF), to offer optimal estimations of these components in order to improve the dynamic performance of Direct Torque Control (DTC) of induction motor drives. The selection and quality of EKF covariance elements have a considerable bearing on the effectiveness of motor drives. Many EKF-based optimization techniques involve only a single objective for the optimal estimation of speed without giving concern to the other variables. In addition, the optimization is performed on a complicated EKF structure. Nevertheless, in this study, both speed and torque are concurrently estimated. The work presents a new method to investigate the selection of EKF filters by using a Non-Dominated Sorting Genetic Algorithm-II (NSGA-II) developed for resolving problems with multiobjectives. Filter element selection is the process of improving the concurrent estimation of speed and torque in order to increase EKF accuracy and allow higher drive efficiency. The proposed multi-optimal EKF-based estimation observer is used in combination with the sensorless direct torque control of induction motor. The investigated results for the multi-objective optimization indicate that the speed optimization gives superior performance when compared to the optimal torque. Owing to the large computation time of EKF algorithm, it increases the sampling time of DTC which leads to an increase in the motor torque ripples. The thesis proposes a Constant Frequency Torque Controller (CFTC) to replace the hysteresis torque controller that offers constant switching frequency and reduces torque ripples. Moreover, the CFTC has the capability of continuous switching regardless of speed variation; hence, leading to a consistent rotation of flux. Consequently, improvement on speed estimation, particularly at low and zero speed regions is accomplished and enhancement on the dynamic performance of torque is achieved when the reference speed change is applied from 0 rad/s, on the condition that the EKF observer is accurately optimized. To verify the improvements of the proposed methods, simulation and experimentation as well as comparison with the EKF-based DTC with the hysteresis controller are carried out

    Solar array fed synchronous reluctance motor driven water pump : an improved performance under partial shading conditions

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    An improved performance of a photovoltaic (PV) pumping system employing a synchronous reluctance motor (SynRM) under partial shading conditions is proposed. The system does not include the dc-dc converter that is predominantly being utilized for maximizing the output power of the PV array. In addition, storage batteries are also not contained. A conventional inverter connected directly to the PV array is used to drive the SynRM. Further, a control strategy is proposed to drive the inverter so that the maximum output power of the PV array is achieved while the SynRM is working at the maximum torque per Ampere condition. Consequently, this results in an improved system efficiency and cost. Moreover, two maximum power point tracking (MPPT) techniques are compared under uniform and partial shadow irradiation conditions. The first MPPT algorithm is based on the conventional perturbation and observation (P&O) method and the second one uses a differential evolution (DE) optimization technique. It is found that the DE optimization method leads to a higher PV output power than using the P&O method under the partial shadow condition. Hence, the pump flow rate is much higher. However, under a uniform irradiation level, the PV system provides the available maximum power using both MPPT techniques. The experimental measurements are obtained to validate the theoretical work

    Fault-Tolerant Control of a Flux-switching Permanent Magnet Synchronous Machine

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    Je jasné, že nejúspěšnější konstrukce zahrnuje postup vícefázového řízení, ve kterém každá fáze může být považována za samostatný modul. Provoz kterékoliv z jednotek musí mít minimální vliv na ostatní, a to tak, že v případě selhání jedné jednotky ostatní mohou být v provozu neovlivněny. Modulární řešení vyžaduje minimální elektrické, magnetické a tepelné ovlivnění mezi fázemi řízení (měniče). Synchronní stroje s pulzním tokem a permanentními magnety se jeví jako atraktivní typ stroje, jejíž přednostmi jsou vysoký kroutící moment, jednoduchá a robustní konstrukce rotoru a skutečnost, že permanentní magnety i cívky jsou umístěny společně na statoru. FS-PMSM jsou poměrně nové typy střídavého stroje stator-permanentní magnet, které představují významné přednosti na rozdíl od konvenčních rotorů - velký kroutící moment, vysoký točivý moment, v podstatě sinusové zpětné EMF křivky, zároveň kompaktní a robustní konstrukce díky umístění magnetů a vinutí kotvy na statoru. Srovnání výsledků mezi FS-PMSM a klasickými motory na povrchu upevněnými PM (SPM) se stejnými parametry ukazuje, že FS-PMSM vykazuje větší vzduchové mezery hustoty toku, vyšší točivý moment na ztráty v mědi, ale také vyšší pulzaci díky reluktančnímu momentu. Pro stroje buzené permanentními magnety se jedná o tradiční rozpor mezi požadavkem na vysoký kroutící moment pod základní rychlostí (oblast konstantního momentu) a provozem nad základní rychlostí (oblast konstantního výkonu), zejména pro aplikace v hybridních vozidlech. Je předložena nová topologie synchronního stroje s permanentními magnety a spínaným tokem odolného proti poruchám, která je schopná provozu během vinutí naprázdno a zkratovaného vinutí i poruchách měniče. Schéma je založeno na dvojitě vinutém motoru napájeném ze dvou oddělených vektorově řízených napěťových zdrojů. Vinutí jsou uspořádána takovým způsobem, aby tvořila dvě nezávislé a oddělené sady. Simulace a experimentální výzkum zpřesní výkon během obou scénářů jak za normálního provozu, tak za poruch včetně zkratových závad a ukáží robustnost pohonu za těchto podmínek. Tato práce byla publikována v deseti konferenčních příspěvcích, dvou časopisech a knižní kapitole, kde byly představeny jak topologie pohonu a aplikovaná řídící schémata, tak analýzy jeho schopnosti odolávat poruchám.It has become clear that the most successful design approach involves a multiple phase drive in which each phase may be regarded as a single-module. The operation of any one module must have minimal impact upon the others, so that in the event of that module failing the others can continue to operate unaffected. The modular approach requires that there should be minimal electrical, magnetic and thermal interaction between phases of the drive. Flux-Switching permanent magnet synchronous machines (FS-PMSM) have recently emerged as an attractive machine type virtue of their high torque densities, simple and robust rotor structure and the fact that permanent magnets and coils are both located on the stator. Flux-switching permanent magnet (FS-PMSM) synchronous machines are a relatively new topology of stator PM brushless machine. They exhibit attractive merits including the large torque capability and high torque (power) density, essentially sinusoidal back-EMF waveforms, as well as having a compact and robust structure due to both the location of magnets and armature windings in the stator instead of the rotor as those in the conventional rotor-PM machines. The comparative results between a FS-PMSM and a traditional surface-mounted PM (SPM) motor having the same specifications reveal that FS-PMSM exhibits larger air-gap flux density, higher torque per copper loss, but also a higher torque ripple due to cogging -torque. However, for solely permanent magnets excited machines, it is a traditional contradiction between the requests of high torque capability under the base-speed (constant torque region) and wide speed operation above the base speed (constant power region) especially for hybrid vehicle applications. A novel fault-tolerant FS-PMSM drive topology is presented, which is able to operate during open- and short-circuit winding and converter faults. The scheme is based on a dual winding motor supplied from two separate vector-controlled voltage-sourced inverter drives. The windings are arranged in a way so as to form two independent and isolated sets. Simulation and experimental work will detail the driver’s performance during both healthy- and faulty- scenarios including short-circuit faults and will show the drive robustness to operate in these conditions. The work has been published in ten conference papers, two journal papers and a book chapter, presenting both the topology of the drive and the applied control schemes, as well as analysing the fault-tolerant capabilities of the drive.
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